The invention is related to a device on an adjustable hydrostatic pump for regulating the delivery flow and, as necessary, also the delivery pressure of same. The demands on the control rate of such adjustable pumps have grown considerably. One of the limits for this control rate is determined by the pressure level of the control flow. This is generally ascertained from the inherent delivery flow of the pump; this is also why its pressure can reach, at most, the level of the initial pressure of the pump. At low operating pressure of the pump, this inevitably leads to limitations of the control rate. As remedies, solutions--e.g. according to FIG. 1 of the drawing--are known which connect the control system with an auxiliary pressure source in phases of low operating pressure. This can be an external pressure supply or a pressure storage system which is recharged from the pump's own circulation during the high-pressure phase in the work cycle. However, a disadvantage in these known devices consists in that a high pressure level now also occurs at low operating pressure at the control edge of the pump regulator. The high regulating accuracy of a conventional regulator-- particularly in the flow control at low operating pressure--is accordingly considerably reduced. This results from the fact that the pressure from which the control pressure is obtained no longer has a fixed relationship to the pressure required in the adjusting piston space. The regulating valve must therefore adjust the pressure divider ratio in the decisive position by means of small changes in position by means of its throttle cross section during every fluctuation in load pressure. In so doing, the effective control pressure differential changes, and the accuracy of the delivery flow deviates from the high standard which is in effect when the operating pressure is approximately equal to the control pressure.